Preparation of multiply-branched aliphatic-aromatic polyesters and multiply-branched aliphatic-aromatic polyesters

ABSTRACT

A multiply-branched aliphatic-aromatic polyester and a method for producing that polymer. The method comprises condensing a branching reactant represented by the general formula ##STR1## Each j is 1 or 2, each Ar is independently selected from the group consisting of aromatic and heteroaromatic moieties having a total of ring carbons and heteroatoms of from 5 to about 20, each R 1  is a linking group independently selected from alkyl having from 1 to about 6 carbons, fluoroalkyl having from 1 to about 6 carbons, --O--, --S--, --C.tbd.C--, and ##STR2## Z 1  is selected from the group consisting of hydroxyl and --OSi(CH 3 ) 3 , and each Z 2  is independently selected from groups having the structural formula ##STR3## wherein each R 2  is independently selected from the group consisting of hydroxy, chloro, bromo, monovalent alkoxide having from 1 to about 6 carbons, and --O--(CH 2 ) g  --OH, wherein g is an integer from 1 to 3, or Z 1  has the structural formula ##STR4## wherein each R 2  is independently selected from the group consisting of hydroxy, chloro, bromo, monovalent alkoxide having from 1 to about 6 carbons, and --O--(CH 2 ) g  --OH, wherein g is an integer from 1 to 3, and each Z 2  is hydroxyl.

BACKGROUND OF THE INVENTION

The present invention pertains to processes for the preparation ofhighly branched polymers and aliphatic-aromatic polyesters. Moreparticularly, the present invention pertains to multiply-branchedpolyesters and processes for the preparation of multiply-branchedaliphatic-aromatic polyesters.

Highly branched, non-crosslinked polymers have been prepared by"multiple generation" and "single generation" procedures. The multiplegeneration procedures are exemplified by Tomalia, D. A., et al,Angewandte Chemie, International Edition in English, 29, 138-175 (1990)and U.S. Pat. No. 5,041,516 to Frechet, J. M. J. et al, which describethe preparation of highly branched, non-crosslinked polyamidoamines andpolybenzyl ethers, respectively. Tomalia et al identified the polymersproduced as "starburst polymers" or "starburst dendrimers". Bothpublications describe preparations in which the macromolecules wereprepared by repeatedly reacting, isolating and purifying a productthrough a series of growth steps. The product of each growth step iscalled a "generation". These procedures are highly laborious, but theproduct produced is highly uniform. Newkome et al, Journal of theAmerican Chemical Society, Vol. 112, 8458, (1990) describes a similarstep and repeat process used to build up various macromoleculesdescribed as tree-like and identified as "arborols".

Single generation procedures are much less laborious than multiplegeneration procedures. The single generation procedures are exemplifiedby Flory, P. J., Journal of the American Chemical Society, 74, p.2718(1952), which presents a theoretical analysis of the formation of highlybranched, soluble polymers from monomers having the structure AB_(x), inwhich A and B are the reactive groups, by step-growth polymerization,with random branching and without cross-linking. Kim, Y. H. et al,Journal of the American Chemical Society, Vol. 112, p. 4592 (1990) andU.S. Pat. No. 4,857,630 to Y. H. Kim, describe this kind of "singlegeneration" approach in the preparation of hyperbranched polyphenylenes.U.S. Pat. No. 3,669,939 to Baker, A. S. et al teaches highly branched,non-crosslinked, aliphatic polyesters, prepared by a "single generation"melt condensation polymerization of monomers having a single carboxylicacid functionality and multiple alcohol functionalities. Hawker, C. J.,Lee, R. and Frechet, M. J. M., Journal of the American Chemical Society,Vol. 113, No. 12, (1991) pp 4583-4588, teaches a single generationprocedure for the preparation of all aromatic, highly-branched,non-cross-linked polyesters. In this procedure,3,5-bis(trimethylsiloxy)benzoyl chloride is melt polymerized by theKricheldorf method, described in H. R. Kricheldorf et al, Makromol.Chem. 184, 475 (1983), driving off trimethylsilylchloride. The productcan be subjected to hydrolysis to provide phenolic terminated highlybranched polyesters. This procedure has the shortcomings of requiringexpensive, water-sensitive reactants and difficult monomer preparationsteps. U.S. patent application Ser. No. 788,070, filed Nov. 11, 1991, byS. Richard Turner et al, teaches the preparation of multiply-branchedpolyesters by reacting compounds having the general structureHOOC--Ar--(O--CO--alkyl) (2 or 3) or having the general structurealkyl-CO--O--Ar--(COOH) (2 or 3). The above-discussed all-aliphaticbranched polyesters of Baker et al and all-aromatic polymers of Hawkerand Frechet et al and Turner et al have extremely divergent Tg's. Theall-aliphatic polymers have very low Tg's, which limits usetemperatures. The all-aromatic polymers have very high Tg's, which makesmelt condensation and various polymer processing procedures difficult.

SUMMARY OF THE INVENTION

The invention provides for highly-branched structures of high molecularweight having useful terminal groups and moderate Tg's in a useful rangefor melt condensation and polymer processing and has the advantages ofnot requiring multiple generations of reactions and purifications or theuse of trimethylsilyl benzoic acid chlorides. The invention, in itsbroader aspects, provides an improved method for producing amultiply-branched polymer comprising condensing a branching reactantrepresented by the general formula ##STR5## Each j is 1 or 2, each Ar isindependently selected from the group consisting of aromatic andheteroaromatic moieties having a total of ring carbons and heteroatomsof from 5 to about 20, each R¹ is a linking group independently selectedfrom alkyl having from 1 to about 6 carbons, fluoroalkyl having from 1to about 6 carbons, --O--, --S--, --C.tbd.C--, and ##STR6## Z¹ isselected from the group consisting of hydroxyl and --OSi(CH₃)₃, and eachZ² is independently selected from groups having the structural formula##STR7## wherein each R² is independently selected from the groupconsisting of hydroxy, chloro, bromo, monovalent alkoxide having from 1to about 6 carbons, and --O--(CH₂)_(g) --OH, wherein g is an integerfrom 1 to 3, or Z¹ has the structural formula ##STR8## wherein each R²is independently selected from the group consisting of hydroxy, chloro,bromo, monovalent alkoxide having from 1 to about 6 carbons, and--O--(CH₂)_(g) --OH, wherein g is an integer from 1 to 3, and each Z² ishydroxyl.

DESCRIPTION OF A SPECIFIC EMBODIMENT

The method of producing multiply-branched aliphatic-aromatic polyestersof the invention utilizes a condensation of a "branching reactant",which can be a single compound or mixture of two or more compounds. Eachof the compounds in branching reactant has the general structure##STR9##

Z¹ and Z² are groups which will react together to form an ester linkage.One of Z¹ and Z² has the general structure ##STR10## in which each R² isindependently selected from the group consisting of hydroxy, chloro,bromo, monovalent alkoxide having from 1 to about 6 carbons, and--O--(CH₂)_(g) --OH, wherein d is an integer from 1 to 3. The other oneof Z¹ and Z² is selected from --OH and --OSi(CH₃)₃.

Each j is independently 1 or 2.

Each R¹ is a linking group independently selected from alkyl having from1 to about 6 carbons, fluoroalkyl having 1 to about 6 carbons, --O--,--S--, --C.tbd.C--, and ##STR11##

Each Ar is independently selected and is an aryl or heteroaryl grouphaving from 1 to 3, five or six membered rings. The rings are solitaryor linked or fused. Ar can have other additional substituents, so longas those substituents do not have a deleterious effect, for example,condensation with Z¹ or Z² groups or steric hindrance or electronicdeactivation of the condensation polymerization. For example, additionalsubstituents cannot be hydroxyls, esters, aminos or sulfonic acids,since those groups would condense with --CO--R². Acceptable substituentsinclude: chloro; fluoro; cycloalkyl; and alkyl, alkoxy, and haloalkyl,all having from 1 to 4 carbons. The --Z² group or groups on a ring canbe can be ortho or meta or para to each other and other ringsubstituents. Linked rings can be joined by a linking group selectedfrom the group consisting of --O--, --S--, ##STR12## Each T¹ isindependently selected from the group consisting of alkyl and aryl, andd is an integer from 1 to 6. Suitable --Ar-- groups include phenyl,thiophene, furan, napthyl, anthracyl, phenanthryl, biphenyl,phenylether, diphenylsulfone, diphenylketone, diphenylsulfide, pyridine,quinoline, and ##STR13##

Repeating units of the multiply-branched polyesters of the invention canbe represented by the five structural formulas, (i)-(v): ##STR14## Inthese formulas, j=1 or 2, Ar and R¹ have the same meaning as above and Qis an ester linkage. If j is replaced by 2 in formulas (i)-(v), eachformula represents a different subunit. If j is replaced by 1 informulas (i)-(v), formulas (iii), (IV), and (v) are redundant, as eachrepresent the same subunit. If one j in formulas (i)-(v) is replaced by1 and the other j is replaced by 2, then formula (IV) is redundant andformula (ii) represents two different subunits: ##STR15## As the aboverepeating unit formulas indicate, condensation of --Z² groups ofnon-terminal repeating units is not complete and many --Z² groups arenon-branched and remain unreacted after the condensation of the methodof the invention. Termini or terminal repeating units have the generalformula ##STR16## A single subunit in each macromolecule of themultiply-branched polyesters of the invention can bear a --Z¹ group inplace of an ester linkage.

For convenience, the branching reactant is generally discussed herein asan individual compound. Using an individual compound in the method ofthe invention produces a multiply-branched polymer which is analogous toa homopolymer, that is, although the repeating units in a macromoleculehave the above-noted differences, each of those repeating units isderived from the same compound. The method of the invention is notlimited to such "homopolymers". Mixtures of two or more compounds can beused as the branching reactant, to produce a multiply-branched polymeranalogous to a copolymer. Relative percentages of the differentcompounds used can be varied. The compounds can differ, for example, in--Z¹ and --Z² groups, in aromatic residues, in placement of --Z² groupson aromatic residues, in --R¹ groups, in R² groups, in values of j, orin a combination of features.

In a particular embodiment of the invention, the method of invention islimited to what can be referred to as a "self-condensation" of thebranching reactant. The term "self-condensation" describes thecondensation of subunits of the branching reactant with each other.Those subunits can be contributed by one compound or a mixture ofcompounds. In an alternative embodiment of the invention, the branchingreactant is self-condensed and co-condensed with a non-branchingreactant, which has the general structure Z¹ --Ar--(--Z²)e, in which eis 0 or 1. If e is 0, the non-branching reactant provides "end-capping"repeating units which terminate branches of the multiply-branchedpolymer. If e is 1, the non-branching reactant provides additionallinear repeating units in the multiply-branched polymer. The end-cappedtermini and additional linear repeating units are, in effect, defects inthat branching is reduced. Defects are desirably kept to a smallpercentage of repeating units. The polymers of the invention do notinclude a percentage of non-branching repeating units great enough todestroy multiple branching in the polymer and produce a polymer in whichbranches do not themselves also branch.

It is necessary that a selected reactant polymerize under the reactionconditions employed. It is desirable that the reactants be sufficientlystable under the reaction conditions employed and that the reactants befree of groups which unduly retard the reaction by steric hindrance orother means. It is also desirable that the reactants not be subject toan unacceptable amount of undesirable side reactions, to prevent theformation of an unacceptable amount of by-product, for example, anunacceptable amount of linear repeating units.

The accessible terminal groups of the multiply-branchedaliphatic-aromatic polyesters can be reacted to modify the accessibleterminal groups or attach other molecules to the termini or tocross-link the termini either within a polymer molecule or betweenpolymer molecules. Suitable reactions are those of equivalent terminalgroups of linear polyesters, such as: ester formation, amide formation,and urethane formation. Functional groups that can be thus provided astermini of the multiply-branched aliphatic-aromatic polyesters include:phenol; carboxylic acid; carboxylic acid chloride, perfluorinated arylor alkyl; primary, secondary and tertiary amine groups; aryl halidessuch as --Cl, --Br, and --I; and benzyl chloride groups. Polymers can bejoined to termini to provide star copolymers in which polymer arms aregrafted to termini of the multiply-branched aliphatic-aromatic polyestercore. Particularly convenient polymers for grafting are those having--OH, --NH₂, --COOH, --Cl, --Br, and --I end groups, which can be joinedto terminal acetoxy, phenol or carboxyl groups by reactions well knownto those skilled in the art.

The method of the invention can be conducted in the presence of acatalyst to enhance the rate of reaction. Catalysts useful in the methodof the invention include condensation catalysts useful in the productionof linear polyesters; for example: Mg, MgO, titanium compounds such astitanium(IV)butoxide and TiO₂ and tin compounds having the generalstructure Sn(R)₄, such as dibutyl tin diacetate. A catalytic amount ofcatalyst is employed. By "catalytic amount" is meant an amount ofcatalyst which catalyzes the reaction to the desired extent. Generally,the amount of catalyst is at least about 0.005 mole percent based on themolar amount of reactant. There is no real upper or lower limit on theamount of catalyst, this being defined by secondary considerations suchas cost and ease of separation of the catalyst from products andunreacted reactants. A preferred catalytic amount is from about 0.01 toabout 1.0 mole percent based upon the molar amount of reactant. Thecatalyst can be bound to a support or unsupported.

The polymerization reaction is preferably carried out in the absence ofsolvent by merely heating the reactant. The polymerization reaction canbe conducted in the presence of solvent, which appreciably dissolvesreactants to provide a liquid reaction medium. The use of solvent slowsthe rate of reaction, in comparison to a melt polymerization. If solventis used, it is desirable that the solvent be "inert" to the reaction,i.e., that the solvent not enter into the reaction in an undesired way.It is desirable that the solvent have a high boiling temperature so thatelevated temperatures can be used in the reaction. The invention is notlimited to a particular solvent or solvent system and a wide variety ofsolvents can be used. Examples of solvents are dimethylformamide andtetramethylenesulfone. The amount of solvent present is not critical,however, practical limits are imposed by the reduced reaction rate, theease of separation of product from the reaction medium, cost and otherfactors. The reaction can also be carried out in the presence of a highboiling non-solvent or diluent such as biphenyl or Marlotherm-S. Thepurpose of this medium is to aid in heat transfer and processability ofthe polymerization monomer.

During the polymerization reaction the small molecule eliminationproduct of the --R² group is produced and evolves from the reaction meltor solution or mixture. For example, if --R² is --O--CH₃, then methanolis produced. Removal of the H--R² provides a driving force forcompletion of the polymerization reaction. The H--R² can be removed bypassing a stream of an inert gas such as nitrogen or argon over orthrough the reaction mass at atmospheric or superatmospheric pressure oralternatively by applying a vacuum to the reaction apparatus or byreacting H--R² to produce a precipitate or the like. For example, if R²is Cl, the H--R² can be removed by reacting the H--R² with amacromolecular base such as polyvinylpyridine. The H--R² may becollected for some other use. As a skilled practitioner will recognize,the specific means used to drive the polymerization reaction is notcritical.

A suitable reaction temperature for the method of the invention, affordsa reasonable rate of reaction and does not give an undue amount ofdecomposition of products or reactants or solvent. The polymerizationreaction is generally conducted at a temperature above about 130° C.Although the reaction can be conducted at temperatures below 130° C.,the polymerization reaction is much slower and molecular weight ofproduct may be reduced. Non-reactive diluents can be used to conduct thepolymerization at a reasonable rate at a lower temperature. The uppertemperature limit on the polymerization reaction is determined bydecomposition temperatures. A suitable temperature range is 140°-280° C.The process of this invention is preferably conducted at a temperaturewithin the range of from about 140° C. to about 250° C.

The reaction time is not a truly independent variable but is dependentat least to some extent on the other reaction parameters selected suchas the reactivity of reactant, absence or presence of catalyst, reactiontemperature, physical properties of the desired product and so forth.Generally, reaction times within the range of from about 0.5 to about 60hours are used.

Agitation of the reaction mixture or solution is optional, howeveragitation assists in the production and yield of the polymer. Agitationof the reaction mixture can be accomplished by any known method, such asmechanical stirring.

The polymerization reaction has been carried out in a batch reactionvessel. It is proposed that the polymerization reaction could be carriedout as a continuous or semi-continuous process. It is further proposedthat it might be preferred that the polymerization reaction would beconducted on a continuous basis as a melt in a continuous stagedreactor. In that continuous process, an inert gas, such as nitrogen orargon could be passed though the melt, preferably in a countercurrentdirection, thereby accomplishing agitation and mixing of the reactionmelt and at the same time removing the small molecule evolved.Alternatively, in that continuous process, a vacuum could be applied tothe reactor to remove the alcohol as it is generated.

The multiply-branched aliphatic-aromatic polyesters of the invention canbe used as coatings, additives, carriers and the like. Specific usesdepend upon the nature of the terminal groups, which can be readilymodified by a wide variety of reactions well known to those skilled inthe art. For example, polymers of the invention having hydroxyl terminalgroups are soluble in various organic solvents and can be used as highsolids industrial coatings. Other polymers of the invention have COOHterminal groups, which can be converted to COO⁻ (Metal)+ groups toprovide ionomers that are soluble in aqueous media and can be used forcoatings and additives.

The following examples are presented for a further understanding of theinvention:

EXAMPLE 1

1,5-Bis(4-carboxyphenyl)-3-pentanol was prepared by the method in U.S.Pat. No. 5,025,086, issued Jun. 18, 1991 to Blount, Jr. et al., column10 lines 25 to 68 and column 13, lines 1 to 35.1,5-Bis(4-carboxyphenyl)-3-pentanol (10 grams) was placed into acondensation polymerization flask under argon. The flask was evacuated,flushed with argon twice to remove air and placed in an oil bath at 235°C. After the monomer melted, three drops (approximately 0.15milliliters) of tin dibutyldiacetate was added as catalyst. The melt wasmaintained at 235° C. under a slow nitrogen stream for 3 hours. Vacuumwas then applied (2×10⁻² torr)(metric) for 1 hour to remove water whichwas formed. The vacuum was then raised to 7×10⁻⁴ torr (metric) andmaintained for an additional 2 hours. On cooling, a glassy polymer wasobtained at a quantitative yield. Tg was determined to be 105° C. Inorder to protect the polymer product during molecular weightdetermination, the polymer was reacted withN-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide (MTBSTFA) toconvert carboxyl groups to dimethyl-t-butylsilylester groups. Molecularweight data were obtained with a size exclusion chromatography (SEC)system using coupled low angle laser light scattering, differentialviscometry and refractive index detection and having three 7.5 mmm.i.d.× 300 mm. 10 micrometer particle diameter PLgel mixed-bed columnsmarketed by Polymer Laboratories of Amherst, Mass. coupled in seriescalibrated against universal calibration standards in tetrahydrofuran.The weight average molecular weight, M_(w), after conversion of carboxylgroups with MTBSTFA was determined to be 11,000. Proton nuclear magneticresonance (NMR) was performed on a 300 MHz GE instrument usingdeuterated dimethylsulfoxide (DMSO-d₆) gave the following peaks (inparts per million (ppm)): 1.9 (b,4H), 2.6 (b,4H), 5.0 (b,1H), 7.25(b,4H), 7.92 (b,4H), 12.75 (b,1H,COOH).

While specific embodiments of the invention have been shown anddescribed herein for purposes of illustration, the protection affordedby any patent which may issue upon this application is not strictlylimited to a disclosed embodiment; but rather extends to allmodifications and arrangements which fall fairly within the scope of theclaims which are appended hereto:

What is claimed is:
 1. A method for a multiply-branched polymercomprising the step of condensing a branching reactant represented bythe general formula ##STR17## wherein each j is 1 or 2,each Ar isindependently selected from the group consisting of aromatic andheteroaromatic moieties having a total of ring carbons and heteroatomsof from 5 to about 20, each R¹ is a linking group independently selectedfrom the group consisting of alkyl having from 1 to about 6 carbons,fluoroalkyl having from 1 to about 6 carbons, --O--, --S--, --C.tbd.C--,and ##STR18## Z¹ is hydroxyl or --OSi(CH₃)₃, and each Z² isindependently selected from groups having the structural formula##STR19## wherein each R² is independently selected from the groupconsisting of hydroxy, chloro, bromo, monovalent alkoxide having from 1to about 6 carbons, and --O--(CH₂)_(g) --OH, wherein g is an integerfrom 1 to 3, or Z¹ has the structural formula ##STR20## wherein each R²is independently selected from the group consisting of hydroxy, chloro,bromo, monovalent alkoxide having from 1 to about 6 carbons, and--O--(CH₂)_(g) --OH, wherein g is an integer from 1 to 3, and each Z² ishydroxyl.
 2. The method of claim 1 wherein Ar has from 2 to 3 rings,said rings each having 5 or 6 members, two of said rings being joined bya linking group selected from the group consisting of --O--, --S--,--(CF₂)_(z) --, ##STR21## wherein each T¹ is independently selected fromthe group consisting of alkyl and aryl, and z is an integer from 1 toabout
 6. 3. The method of claim 1 wherein Ar is a divalent or trivalentmoiety selected from the group consisting of phenyl, thiophene, furan,naphthalene, anthracene, phenanthrene, biphenyl, phenylether,diphenylsulfone, diphenylketone, diphenylsulfide, ##STR22## pyridine,quinoline, and
 4. The method of claim 1 wherein said condensation is anequilibrium reaction and further comprising driving the equilibrium ofsaid condensation toward said multiply-branched polyesters.
 5. Themethod of claim 1 further comprising removing small molecule by-productproduced during said condensation.
 6. A method for producing amultiply-branched polymer comprising the step of condensing Z¹ and Z²groups of a reactant having the general formula ##STR23## wherein j is 1or 2,each Ar is an aryl or heteroaryl group including from 1 to 3,solitary or linked or fused, five or six membered rings, each R¹ is alinking group independently selected from the group consisting of alkylhaving from 1 to about 6 carbons, fluoroalkyl having from 1 to about 6carbons, --O--, --S--, --C.tbd.C--, and ##STR24## and one of Z¹ and Z²is hydroxyl, and the other one is independently selected from groupshaving the structural formula ##STR25## wherein each R² is independentlyselected from the group consisting of hydroxy, chloro, bromo, monovalentalkoxide having from 1 to about 6 carbons, --O--(CH₂)_(g) --OH, whereing is an integer from 1 to
 3. 7. A method for producing amultiply-branched polymer comprising the step of condensing a branchingreactant having the general formula ##STR26## wherein d and e are eachintegers from 1 to about 11 and d+e is from 2 to about 12,each Ar isindependently selected from the group consisting of aromatic andheteroaromatic moieties having a total of ring carbons and heteroatomsof from 5 to about 20, and each R² is independently selected from thegroup consisting of hydroxy, chloro, bromo, monovalent alkoxide havingfrom 1 to about 6 carbons, and --O--(CH₂)_(g) --OH, wherein g is aninteger from 1 to
 3. 8. The method of claim 7 wherein said condensationis incomplete as to non-terminal repeating units of saidmultiply-branched polyester.
 9. The method of claim 7 wherein individualmonomer units of said reactant are condensed as to zero, or one, or morethan one ##STR27##
 10. The method of claim 7 wherein said reaction isconducted in the presence of a catalyst for a condensation reactionhaving as a product linear polyester.
 11. The method of claim 7 whereinsaid reaction is conducted at a temperature between about 140° C. andabout 250° C.
 12. A multiply branched aliphatic-aromatic polyesterhaving repeating units represented by the general formulas: ##STR28##wherein Q is an ester linkage,each j is 1 or 2, each Ar is independentlyselected from the group consisting of aromatic and heteroaromaticmoieties having a total of ring carbons and heteroatoms of from 5 toabout 20, each R¹ is a linking group independently selected from thegroup consisting of alkyl having from 1 to about 6 carbons, fluoroalkylhaving from 1 to about 6 carbons, --O--, --S--, --C.tbd.C--, and##STR29## and Z¹ is selected from the group consisting of hydroxyl and--OSi(CH₃)₃, and each Z² is independently selected from the group ofmoieties having the structural formula ##STR30## wherein each R² isindependently selected from the group consisting of hydroxy, chloro,bromo, monovalent alkoxide having from 1 to about 6 carbons, and--O--(CH₂)_(g) --OH, wherein g is an integer from 1 to 3, or Z¹ has thestructural formula ##STR31## wherein each R² is independently selectedfrom the group consisting of hydroxy, chloro, bromo, monovalent alkoxidehaving from 1 to about 6 carbons, and --O--(CH₂)_(g) --OH, wherein g isan integer from 1 to 3, and each Z² is hydroxyl.